Install dependencies:
sudo apt install git gtk2-engines-murrine gtk2-engines-aurora
sudo pacman -S git gtk-engine-murrine --needed
sudo dnf install git gtk-murrine-engine
Open terminal and type line below:
git clone https://github.com/Romchec/elementary-OS-gtk2-support.git && cd elementary-OS-gtk2-support && sudo ./install.sh && cd .. && rm -rf elementary-OS-gtk2-support
Now switch to another accent color and then switch it back again.